04.Eclipse下Ndk开发（以文件拆分合并为例模拟一下开发过程，参考文件加密的过程）
(创建于2017/12/6) 1.工具类PatchUtils package com.ren.ndk_file_patch; public class PatchUtils { static{ System.loadLibrary("ndk_file_patch"); } public native static void diff(String path,String path_pattern,int count); public native static void patch(String path_pattern,String merge_path,int count); } 2.生成的头文件 com_ren_ndk_file_patch_PatchUtils.h /* DO NOT EDIT THIS FILE - it is machine generated */ #include <jni.h> /* Header for class com_ren_ndk_file_patch_PatchUtils */ #ifndef _Included_com_ren_ndk_file_patch_PatchUtils #define _Included_com_ren_ndk_file_patch_PatchUtils #ifdef __cplusplus extern "C" { #endif /* * Class: com_ren_ndk_file_patch_PatchUtils * Method: diff * Signature: (Ljava/lang/String;Ljava/lang/String;I)V */ JNIEXPORT void JNICALL Java_com_ren_ndk_1file_1patch_PatchUtils_diff (JNIEnv *, jclass, jstring, jstring, jint); /* * Class: com_ren_ndk_file_patch_PatchUtils * Method: patch * Signature: (Ljava/lang/String;Ljava/lang/String;I)V */ JNIEXPORT void JNICALL Java_com_ren_ndk_1file_1patch_PatchUtils_patch (JNIEnv *, jclass, jstring, jstring, jint); #ifdef __cplusplus } #endif #endif 3.编写的c文件 ndk_file_patch.c #include "com_ren_ndk_file_patch_PatchUtils.h" #include <jni.h> #include <stdio.h> #include <stdlib.h> #include<android/log.h> #define LOGI(FORMAT,...) __android_log_print(ANDROID_LOG_INFO,"renzhenming",FORMAT,__VA_ARGS__); #define LOGE(FORMAT,...) __android_log_print(ANDROID_LOG_ERROR),"renzhenming",FORMAT,__VA_ARGS__); long get_file_size(const char *path){ FILE *fl = fopen(path,"rb"); //把与fp有关的文件位置指针放到一个指定位置。 //文件指针定位到文件末尾，偏移0个字节 fseek(fl,0,SEEK_END); //函数用来获取文件读写指针的当前位置,对于二进制文件，则返回从文件开头到结尾的字节数。 return ftell(fl); } JNIEXPORT void JNICALL Java_com_ren_ndk_1file_1patch_PatchUtils_diff (JNIEnv *env, jclass jclz, jstring path_jstr, jstring path_pattern_jstr, jint file_num){ //转换文件路径 const char *path = (*env)->GetStringUTFChars(env,path_jstr,NULL); const char *path_pattern = (*env)->GetStringUTFChars(env,path_pattern_jstr,NULL); //得到分割之后的所有文件路径 //申请一段连续的内存空间（一个数组）保存所有分割的文件地址 char **patches = malloc(sizeof(char*)*file_num); int i = 0; for(;i<file_num;i++){ patches[i]=malloc(sizeof(char)*100); //元素赋值 //需要分割的文件：C://jason/liuyan.png //子文件：C://jason/liuyan_%d.png(path_pattern的格式) sprintf(patches[i],path_pattern,(i+1)); LOGI("patch path:%s",patches[i]); } //不断读取path文件，循环写入file_num个文件中 // 整除 // 文件大小：90，分成9个文件，每个文件10 // 不整除 // 文件大小：110，分成9个文件， // 前(9-1)个文件为(110/(9-1))=13 // 最后一个文件(110%(9-1))=6 //获取文件大小 int file_size = get_file_size(path); //打开这个文件 FILE *fpr = fopen(path,"rb"); //整除 if(file_size % file_num == 0){ //单个文件大小 int part = file_size/file_num; int i =0; //逐一写入设置好的子文件路径中 for(;i<file_num;i++){ //从子文件路径打开一个FILE FILE *fpw = fopen(patches[i],"wb"); int j = 0; for(;j<part;j++){ //边读边写 //fgetc函数功能：从流中读取字符，即从fp所指定的文件中取得下一个字符。这里需要注意，在每取完一个字符时fp会自动向下移动一个字节。这样编成时，程序员就不用再对fp //控制了。这种功能在许多读写函数中都有体现。 fputc(fgetc(fpr),fpw); } fclose(fpw); } }else{ //无法整除 int part = file_size/(file_num-1); int i = 0; for(;i<file_num-1;i++){ FILE *fpw = fopen(patches[i],"wb"); int j=0; for(;j<part;j++){ fputc(fgetc(fpr),fpw); } fclose(fpw); } //最后一个子文件 FILE *fpw = fopen(patches[file_num-1],"wb"); i = 0; for(;i<file_size%(file_num-1);i++){ fputc(fgetc(fpr),fpw); } fclose(fpw); } //释放 i = 0; for(;i<file_num;i++){ free(patches[i]); } free(patches); (*env)->ReleaseStringUTFChars(env,path_jstr,path); (*env)->ReleaseStringUTFChars(env,path_pattern_jstr,path_pattern); } /* * Class: com_ren_ndk_file_patch_PatchUtils * Method: patch * Signature: (Ljava/lang/String;Ljava/lang/String;I)V */ JNIEXPORT void JNICALL Java_com_ren_ndk_1file_1patch_PatchUtils_patch (JNIEnv *env, jclass jclz, jstring path_pattern_jstr, jstring merge_path_jstr, jint file_num){ //字符串转换 const char *merge_path = (*env)->GetStringUTFChars(env,merge_path_jstr,NULL); const char *path_pattern = (*env)->GetStringUTFChars(env,path_pattern_jstr,NULL); //得到分割后的子文件路径列表 char **patches = malloc(sizeof(char*)*file_num); int i = 0; for(;i<file_num;i++){ patches[i]=malloc(sizeof(char)*100); //元素赋值 //需要分割的文件：C://jason/liuyan.png //子文件：C://jason/liuyan_%d.png sprintf(patches[i],path_pattern,i+1); LOGI("patch path:%s",patches[i]); } //打开要merge_path为一个FILE FILE *fpw = fopen(merge_path,"wb"); //把所有分割的文件读取一遍，写入到这个总的文件中 i = 0; for(;i<file_num;i++){ //得到每个子文件的大小 int file_size = get_file_size(patches[i]); //打开每个子文件路径为一个FILE FILE *fpr = fopen(patches[i],"rb"); int j =0; for(;j<file_size;j++){ fputc(fgetc(fpr),fpw); } fclose(fpr); } fclose(fpw); //释放内存 i = 0; for(;i<file_num;i++){ free(patches[i]); } free(patches); (*env)->ReleaseStringUTFChars(env,merge_path_jstr,merge_path); (*env)->ReleaseStringUTFChars(env,path_pattern_jstr,path_pattern); } 4.Android.mk文件 LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE := ndk_file_patch LOCAL_SRC_FILES := ndk_file_patch.c LOCAL_LDLIBS := -llog //使用了log，需要引入 include $(BUILD_SHARED_LIBRARY) 5.开始拆分合并 public class MainActivity extends Activity { private String SD_CARD_PATH; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); SD_CARD_PATH = Environment.getExternalStorageDirectory().getAbsolutePath(); } public void diff(View view){ String path = SD_CARD_PATH +File.separatorChar+ "2.mp4"; String path_pattern = SD_CARD_PATH +File.separatorChar+ "2_%d.mp4"; PatchUtils.diff(path, path_pattern, 2); System.out.println("拆分完成"); } public void patch(View view){ String merge_path = SD_CARD_PATH +File.separatorChar+ "2_new.mp4"; String path_pattern = SD_CARD_PATH +File.separatorChar+ "2_%d.mp4"; PatchUtils.patch(path_pattern, merge_path, 2); System.out.println("合并完成"); } } 6.注意添加权限，6.0动态申请 <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
